Why does C++ not have reflection?

Question

This is a somewhat bizarre question. My objectives are to understand the language design decision and to identify the possibilities of reflection in C++. 1. Why C++ language committee did not go towards implementing reflection in the language? Is reflection too difficult in a language that does not run on a virtual machine (like java)? 2. If one were to implement reflection for C++, what will be the challenges? I guess the uses of reflection are well-known: editors can be more easily written, program code will be smaller, mocks can be generated for unit tests and so on. But it would be great if you could comment on uses of reflection too.

Answer 1

The C programming language was originally developed to write the Unix operating system. The belief was that it was straightforward to write a C compiler for a new processor, then compile Unix for it. At the time, the practice was to develop an OS in assembler separately for each processor architecture and software could not easily migrate from one architecture to another. Java extended this approach by using a standard compiler to generate byte code that was interpreted by a run-time engine specific to the platform.

Doing things differently always presents an opportunity to take advantage of the difference. A compiled C (or C++) object file does not normally carry the type of information needed for reflection. It is foolish to require that one language optimized for one set of purposes conform to a standard set by another language optimized for a different set of purposes. We could revise the format for a C++ obj to include the information needed for reflection. All we would have to do is to recompile 70 or so years of code to use it.